1. Field of the Invention
The present invention relates to a liquid discharge method and a liquid jet apparatus for discharging liquid by use of energy generating devices. More particularly, the present invention relates to a liquid discharge method and a liquid jet apparatus for discharging a desired liquid by the action of bubbles to be created by causing thermal energy to act upon liquid.
2. Related Background Art
There has been known conventionally an ink jet recording method, that is, the so-called bubble jet recording method, which performs the image formation in such a manner that energy, such as heat, is given to ink in the form of pulses in response to recording signals so as to create the change of states in ink with its abrupt voluminal changes to follow, and that ink is discharged from the discharge openings by the acting force based upon this change of states, thus adhering to a recording medium for the formation of images. The recording apparatus that uses this bubble jet recording method is generally provided with discharge openings for discharging ink; ink flow paths conductively connected with the discharge openings; and heat generating devices (electrothermal transducing devices) which are arranged in the ink flow paths as energy generating means for discharging ink as disclosed in the specifications of Japanese Patent Publication No. 61-59911, Japanese Patent Publication No. 61-59914, and U.S. Pat. No. 4,723,129, among some others.
With a recording method of the kind, images can be recorded in high quality at high speeds with a lesser amount of noises. At the same time, the discharge openings of the head can be arranged in high density to carry out this recording method. Therefore, among a number of advantages, this method makes it easier to obtain images in high resolution, and also, color images recorded by use of a smaller apparatus. As a result, the bubble jet recording method has been widely used for a printer, a copying machine, a facsimile equipment, or other office equipment in recent years. Furthermore, this method begins to be adopted even for a textile printing system or other systems for industrial use.
However, for the ink jet recording method, the volume of ink droplet to be discharged per pixel portion is almost constant usually. Therefore, a special device is needed in order to execute a gradation recording. In this respect, there is disclosed in Japanese Patent Laid-Open Application No. 8-230215, for example, an ink jet recording head that discharges a mixture of ink liquid and dilution for printing on a printing medium, hence making a gradation recording possible.
However, in the case of the ink jet recording head disclosed in Japanese Patent Laid-Open Application No. 8-23015, it is set forth as a premise that the discharge speed is invariable when ink droplets are discharged from each of the discharge openings. In this laid-open application, there is no disclosure at all as to the exact method for effectuating the collision between ink droplets to be discharged from the ink jet recording head the discharge speed of which tends to fluctuate when actually in use. Also, in order to materialize the gradation recording, two kinds of ink droplets should collide with each other in one case, but not in the other. If the impact positions of ink droplets should be deviated greatly on a recording medium depending on these two deferent cases, it is impossible to obtain any images in high quality at all. Nevertheless, there is no technical disclosure on this aspect in the above-mentioned laid-open application.
Now, the problems encountered conventionally by the ink jet recording method have been discussed on the execution of the gradation recording so far. However, this operation, that is, two kinds of droplets are discharged and mixed before being impacted on a printing medium or other object, is not necessarily limited to the gradation recording described above.
For example, assuming that a substance C created by the reaction of A+B.fwdarw.C changes to be C' when adhering to an object, there may be a case where the substance C thus created is a material itself which is not stable in the formation of a pattern which is selectively made by the C' that adheres to the object. In such a case, a first droplet containing A and a droplet containing B are discharged separately from different discharge openings and are caused to collide with each other during its flight to the object so that the A and B react upon themselves to create C. Then, immediately after that, the droplet that contains C is impacted on the object and changes to be C'. It is preferable to adopt a structure of the kind from the view point of the positional accuracy or other requirements for the formation of pattern made by the C'. However, in this case, too, there are the problems discussed above still remaining as those should be solved.